In the power generation and distribution industry, utility companies generate electricity and distribute the electricity to customers. To facilitate the process of distributing electricity, various types of power switching devices are used. In a distribution circuit, electricity flows through the power switching devices from a power generation source (typically a substation or the like) to the consumer. When a fault is detected in the distribution circuit, the power switching device is opened and the electrical connection is broken.
Within the power switching device, a magnetic actuator (hereinafter referred to as an “actuator”) is used to provide the mechanical means of opening and closing the distribution circuit. The movement of the actuator pushes or pulls a moveable electrical contact towards or away from a stationary contact. When the electrical contacts touch, the circuit is closed and electricity flows through the power switching device. When the actuator pulls the moveable electrical contact away from the stationary contact, the flow of electricity through the power switching device is interrupted and the circuit is opened. The motion of the moveable contact is in the same direction as the motion of the actuator. This type of actuator is typically referred to as a linear actuator.
Controllers are used by the utility company to detect faults that occur in the distribution circuit. This type of controller typically uses a microprocessor programmed to respond to the fault based on the type of fault and the type of power switching device connected to the controller. The controller may respond to a particular fault by causing the power switching device to remain open. Alternatively, upon the detection of a fault, the controller may cause the power switching device to open and close multiple times.
The controller sends an electrical waveform to a coil in the actuator in one direction to open the distribution circuit and in the opposite direction to close the distribution circuit. The electrical waveform may be a continuous DC waveform or a modulated waveform. If a continuous DC waveform is applied to an open power switching device, the moveable contact starts to accelerate and continues to accelerate up to the point of contact. This causes the moveable contact to slam into the stationary contact with such force that the contacts bounce apart and arcing occurs. Alternatively, a modulated waveform as described in U.S. Pat. No. 6,331,687 may be used. Another way of operating a linear actuator is described in U.S. Pat. No. 6,836,121.
The controller may be programmed from the factory with a default modulated waveform characteristic (amplitude and duration). Alternatively, the modulated waveform may be programmed in the field by a utility craftsperson. The craftsperson uses an interface to the controller to select a preprogrammed waveform to be applied to the coil of the actuator. The prior art modulated waveforms used to control the actuator are of a fixed amplitude and duration throughout the operation of the actuator.
Instead of selecting from a set of standard modulated waveforms, the present invention allows a user to program a specific amplitude and duration for the modulated waveform used to control the actuator coil. The present invention also allows the craftsperson to program a variety of waveforms to be sent to the actuator. One set of waveforms is applied to the coil of the actuator before the moveable contact is set in motion. Another set of waveforms is applied while the moveable contact is in motion, and yet another set of waveforms is applied when the moveable contact has stopped moving. The present invention also allows the controller to automatically modify the user programmed waveforms based on real time operating conditions at the power switching device.